In general, because of their high workability and productivity, mounting methods utilizing soldering are widely used to mount electrical components, such as semiconductor devices on printed wiring boards. When a semiconductor device is mounted on a printed wiring board by soldering, high reflow temperatures cause warping of the semiconductor device and printed wiring board, thus resulting in poor reliability of the mechanical and electrical connection of a solder bonding portion between the semiconductor device and the printed wiring board of the electrical apparatus. Thus, semiconductor devices are soldered to printed wiring boards at low reflow temperatures using solder materials having low melting points. One solder material having a low melting point is an InSn eutectic solder that has a melting point of 117° C. In—Sn alloy solder materials have lower melting points but lower strength than Sn—Bi alloy and Sn—Ag—Cu alloy solder materials. It is proposed that a solder material having a low melting point contains an intermetallic compound in order to increase the strength of the solder material (see, for example, Japanese Laid-open Patent Publications No. 2006-909 and No. 2002-124533). However, even when electrical components are mounted with the solder materials described above, for example, because of insufficient resistance to drop impact on the electrical components, electrical apparatuses have poor reliability of mechanical and electrical connection between the electrical components.